This invention relates to a device and a method for preventing fraudulent copies of data and also to a recording medium. More specifically, this invention relates to a device and a method for preventing fraudulent copies of data on digitized documents, sounds, images and/or programs and also to a recording medium to be suitably used with such a device.
In recent years, the development and commercialization of digital recording/reproducing apparatus has made it possible to transfer data from a such apparatus to another for the purpose of copying without degrading the quality of data particularly in terms of the images and/or the sounds to be reproduced by the data.
However, the ability of copying data without degrading the quality thereof can inevitably entail illegal sales of copies of audio-visual works or pirating, infringing the copyright of the authors of the works. Illegal copies have to be firmly prevented from taking place because it is technologically easy to copy digitized works and distribute copies to indefinite people by means of large capacity digital recording/reproducing apparatus such as D-VCRs and DVD-RAMs. Now, many authors of digitized images and other digitized works share a sense of crisis under these circumstances.
While various techniques may be conceivable for pirating, any pirate has to follow a process of receiving the data for the object of pirating from a data reproducing device such as a DVD-ROM drive or a DVD-ROM and then copying the data by means of a digital recording device such as a DVD-RAM.
There is known a management system called SCMS (serial copy-management system) to be used with digital recording/reproducing apparatus such as DATs and MDs having a capacity smaller than DVDs for preventing fraudulent copies from being made.
Data to copied from a CD to an MD (or a DAT) or from an MD (or a DAT) to another MD (or another DAT) by means of an SCMS carries a piece of copy information added to the data head. The copy information is a 2-bit data. If the copy information on the master disc is xe2x80x9c00xe2x80x9d, any data copied from the master disc will carry the copy information of xe2x80x9c00xe2x80x9d to indicate that it is free for copying.
If, the copy information on the master disc is xe2x80x9c10xe2x80x9d, any data may copied directly from the master disc (to produce a first generation copy) but no data can be copied form the first generation copy (to produce a second generation copy). In other words, when data are copied from the master disc, the copy information carried by the copied data, or the data of the first generation copy, is counted up to become xe2x80x9c11xe2x80x9d and no data can be copied if it carries the copy information of xe2x80x9c11xe2x80x9d so that any second generation copy will be prevented from being produced.
The above described system refers to a method for preventing fraudulent copies by means of a digital recording/reproducing apparatus designed to prevent copies that infringe the copyright of the author of the original from being fraudulently made. However, if each apparatus is provided with anti-fraud measures, a pirate can illegally copy the data being transmitted from an apparatus to another somewhere on the transmission path to make such anti-fraud measures powerless.
As known and popular anti-fraud measures for data transmission, confidential data are often encrypted. Encryption systems are generally categorized as open key systems and secret key systems, although the latter are popularly used when data are to be transmitted and processed at high speed.
For encrypting data by means of a secret key, the two parties at the opposite end of the transmission line talk with each other to determine the secret key to be used for the coming communication in a cryptic system.
Thus, if the secret key is identified by a third party and fraudulently used for pirating, then the two parties will have to select a new secret key to continue the communication to maintain, if not lost, the confidentiality of the data. Thus, there is a need for effective cryptic systems that can be used for data transmission among digital recording/reproducing apparatus.
There is also a need for devices that can effectively prevent fraudulent copies of data. The above cited SCMS allows to produce first generation copies so that pirates can freely produce such copies for sale. Additionally, frauds can forge the copy information of xe2x80x9c00xe2x80x9d to freely make illegal copies.
Therefore, there is a strong need for a copy management method that is more reliable, more elaborate and more realistic than the SCMS and can be applied to large capacity digital recording/reproducing apparatus that potentially involve serious copyright problems.
In view of the above identified circumstances, it is therefore a first object of the present invention to provide a device and a method for effectively and reliably preventing any illegal access to the copy-management information contained in the data to be handled and also to a recording medium to be suitably used with such a device.
A second object of the invention is to provide a device and a method for effectively preventing any fraudulently copied data from being reproduced.
A third object of the invention is to provide a device and a method for preventing fraudulent copies by means of an elaborate copy management system.
According to a first aspect of the invention, the above objects and other objects are achieved by providing a device to be used with digital data copying apparatus for preventing fraudulent copies of a digital data;
the digital data including an encrypted data main body and encrypted copy management information for controlling permission with regard to copying the data main body;
the device comprising:
a determining section for determining if permission be granted for copying the digital data or not based on if the copy management information satisfies predetermined requirements or not; and
a prohibition processing section for prohibiting any operation of effectively copying the digital data when the determining section determines that permission should not be granted for copying the digital data.
According to a second aspect of the invention, there is provided a device to be used with digital data copying apparatus for preventing fraudulent copies of a digital data;
the digital data containing an encrypted data main body, encrypted copy management information for controlling permission with regard to copying the data main body and key information for decrypting the data main body;
the device comprising:
a determining section for determining if permission be granted for copying the digital data or not based on if the copy management information satisfies predetermined requirements or not; and
a key altering section for altering the key information contained in the digital data when the determining section determines that permission should not be granted for copying the digital data.
According to a third aspect of the invention, there is provided a method to be used with digital data copying apparatus for preventing fraudulent copies of a digital data;
the digital data containing an encrypted data main body, encrypted copy management information for controlling permission with regard to copying the data main body and key information for decrypting the data main body;
the method comprising steps of:
determining if permission be granted for copying the digital data or not based on if the copy management information satisfies predetermined requirements or not; and
altering the key information contained in the digital data when the determining section determines that permission should not be granted for copying the digital data.
According to a fourth aspect of the invention, there is provided a method to be used with digital data copying apparatus for preventing fraudulent copies of a digital data comprising steps of:
adding to the digital data copy management information containing generation management information to indicate the generation of the digital data as descendent of the original data and numerical management information to indicate the number of copies made from the digital data;
prohibiting any operation of copying the digital data when the generation management information indicates a predetermined generation and the numerical management information indicates a predetermined number of copies.
According to a fifth aspect of the invention, there is provided a recording medium for storing data having a computer-readable data structure;
the data structure comprising:
an encrypted data main body;
encrypted copy management information for controlling permission with regard to copying the data main body;
first key information for decrypting the data main body; and
second key information for decrypting the copy management information.
According to a sixth aspect of the invention, there is provided a recording medium for storing data having a computer-readable data structure;
the data structure comprising:
an encrypted data main body;
first key information obtained by encrypting a data encryption key to be used for decrypting the data main body;
a plurality of second key information obtained by encrypting the data encryption key by means of a plurality of encryption keys; and
a plurality of third key information obtained by encrypting copy management information for controlling permission with regard to copying the data main body by means of the plurality of encryption keys.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.